Fox411 hears that there could be trouble in paradise for newlywed couple Scarlett Johansson and Ryan Reynolds. The two movie stars were married in a quiet ceremony on a wilderness retreat in Canada on September 27, 2008, and the couple has kept their relationship under lock and key for the last 10 months, but our spies warn of recent arguments and fights. The most heated occurred last week, as they were about to depart for San Diego's Comic Con sci-fi convention.

Scarlett, there to discuss her new role as Black Widow in "Iron Man 2," was set to appear on her panel with Robert Downey Jr. and other cast members. Ryan was just cast as the lead in "Green Lantern," a Warner Brothers flick. An insider tells FOX411 "they got in a huge fight just before they were going to Comic Con. It caused such a rift between them that Ryan refused to attend the conference and he told Scarlett she could go alone. She got so angry she threatened to take off her wedding band."

The conference continued as normal, with a notably absent Ryan missing from the Warner Brothers panel. The company had planned on debuting major plans for the new superhero movie, and now insider says Ryan has "angered the executives." Apparently Scarlett began the fight but came out smelling like rose thanks to her appearance at the conference.

"Ryan pulled out at the last minute and word spread fast. He isn't making a show of good faith to the Warner team after they battled over the decision making him 'Green Lantern'," says our snitch. "Scarlett ended up looking like the true professional and acted as if nothing was wrong, answering questions for fans and posing for pictures. It was not a good way for Ryan to begin his work as the star of the movie."